Letter 4092

How to prevent galling on stainless steel bolts & nuts 

-

I produce pipe couplings and stainless steel clamps.The bolts which tighten the products as the nuts are made of stainless steel 304.I have problems of galling (cold welding).I would like to know what kind of lubricant can use (need to be dry ..or dirt will stick to it while installing the product ).I also need the machine or the process to coat it .

Danny Krausz  
- Tel Aviv, Israel

To prevent galling on type 304 stainless steel we suggest hard chrome plating a deposit of .0003"-.0005" thick.

Stephen C. Ward
- Canada

We use to apply a Teflon coating on the bolts and nuts to prevent galling. It works very well.

Jordi Pujol
- Barcelona

I am considering using 304 Stainless steel bolts to connect aluminum (6061) shape to aluminum (6061) plate. In this application I need to minimize the amount of magnetic material inside my vessel and I cannot use a lubricant because the vessel is under a vacuum. I am concerned about galling. Do I have to chrome plate the fasteners? Is this very expensive? Any other options?

Donald Sokol
- Oak Ridge, TN

Two approaches I have heard of is silver plating the bolts or using Nitronic stainless steel, a grade designed to prevent galling.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

In addition to above methods kindly let me know if Xylan coating of SDSS fasteners also prevent galling

Ravindra Maurya
- Mumbai, India

Hi, Ravindra. Anything that prevents the stainless from contacting the stainless will prevent galling. But for good answers, please try to follow the style of the two previous inquiriers and describe your own situation instead of casting the proposition in the abstract. Thanks.

Regards,

Ted Mooney finishing.com Brick, New Jersey